lkml.org 
[lkml]   [2018]   [Nov]   [8]   [last100]   RSS Feed
Views: [wrap][no wrap]   [headers]  [forward] 
 
Messages in this thread
Patch in this message
/
Date
From
SubjectRe: [PATCH 5/7] mtd: spi_nor: pass DMA-able buffer to spi_nor_read_raw()
On Thu, 8 Nov 2018 11:07:16 +0000
<Tudor.Ambarus@microchip.com> wrote:

> spi_nor_read_raw() calls nor->read() which might be implemented
> by the m25p80 driver. m25p80 uses the spi-mem layer which requires
> DMA-able in/out buffers. Pass kmalloc'ed dma buffer to spi_nor_read_raw().
>
> Signed-off-by: Tudor Ambarus <tudor.ambarus@microchip.com>
> ---
> drivers/mtd/spi-nor/spi-nor.c | 14 ++++++++++----
> 1 file changed, 10 insertions(+), 4 deletions(-)
>
> diff --git a/drivers/mtd/spi-nor/spi-nor.c b/drivers/mtd/spi-nor/spi-nor.c
> index 79ca1102faed..2eaa21c85483 100644
> --- a/drivers/mtd/spi-nor/spi-nor.c
> +++ b/drivers/mtd/spi-nor/spi-nor.c
> @@ -2161,7 +2161,7 @@ spi_nor_set_pp_settings(struct spi_nor_pp_command *pp,
> * @nor: pointer to a 'struct spi_nor'
> * @addr: offset in the serial flash memory
> * @len: number of bytes to read
> - * @buf: buffer where the data is copied into
> + * @buf: buffer where the data is copied into (dma-safe memory)
> *
> * Return: 0 on success, -errno otherwise.
> */
> @@ -2868,11 +2868,16 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
> u8 smpt_len)
> {
> const u32 *ret;
> + u8 *dma_safe;

I'd prefer to have it named buf, data_buf or scratch_buf...

> u32 addr;
> int err;
> u8 i, ncmds, nmaps;
> u8 addr_width, read_opcode, read_dummy;
> - u8 read_data_mask, data_byte, map_id;
> + u8 read_data_mask, map_id;
> +

... and have a comment here explaining why your allocating the buffer
instead of using a local var placed on the stack.

> + dma_safe = kmalloc(sizeof(*dma_safe), GFP_KERNEL | GFP_DMA);

Please don't use GFP_DMA, kmalloc() should already return a DMA-safe
buffer (see [1]).

> + if (!dma_safe)
> + return ERR_PTR(-ENOMEM);
>
> addr_width = nor->addr_width;
> read_dummy = nor->read_dummy;
> @@ -2890,7 +2895,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
> nor->read_opcode = SMPT_CMD_OPCODE(smpt[i]);
> addr = smpt[i + 1];
>
> - err = spi_nor_read_raw(nor, addr, 1, &data_byte);
> + err = spi_nor_read_raw(nor, addr, 1, dma_safe);
> if (err) {
> ret = ERR_PTR(err);
> goto out;
> @@ -2900,7 +2905,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
> * Build an index value that is used to select the Sector Map
> * Configuration that is currently in use.
> */
> - map_id = map_id << 1 | !!(data_byte & read_data_mask);
> + map_id = map_id << 1 | !!(*dma_safe & read_data_mask);
> ncmds++;
> }
>
> @@ -2941,6 +2946,7 @@ static const u32 *spi_nor_get_map_in_use(struct spi_nor *nor, const u32 *smpt,
>
> /* fall through */
> out:
> + kfree(dma_safe);
> nor->addr_width = addr_width;
> nor->read_dummy = read_dummy;
> nor->read_opcode = read_opcode;

[1]https://elixir.bootlin.com/linux/latest/source/include/linux/gfp.h#L263

\
 
 \ /
  Last update: 2018-11-08 14:03    [W:0.153 / U:1.476 seconds]
©2003-2020 Jasper Spaans|hosted at Digital Ocean and TransIP|Read the blog|Advertise on this site